Beginning in the large intestine, colon cancer tends to begin as non-cancerous polyps. These usually have no noticeable symptoms but can be detected via screening. It becomes harder to treat the condition the further it has advanced, making it essential to detect it at the early stages. Staging is a process used to point out the exact extent to which cancer has spread. It provides a structure and clarity to the condition and enables the doctors to decide on the best methods of treatment. The staging guidelines used for colon cancer follow the system on TNM staging which is as follows:

• T – Tumor: This gives information on whether the tumor has grown into the wall of the colon and if it has, then the layers it has spread to.
• N – Node: This gives information on whether the tumor has spread to lymph nodes, and if it has, their location and the number of lymph nodes affected.
• M – Metastasis: This gives information on whether the tumor has spread to other parts of the body, which parts and how much it has affected a particular organ.

These 3 stages are further divided into 5 stages — Stage 0 and Stages 1–4 which delve into greater information regarding the tumor. These stages are as follows:

Tumor:

• TX: Tumor cannot be determined through tests.
• T0: No proof is found for the presence of cancer in the colon
• T1: Cancer cells are found in the topmost layer or lining of the colon, also known as the epithelium.
• T2: The tumor has spread to a deeper and thicker layer of muscle in the colon which as a result shrinks in size to move along the contents of the intestine.
• T3: Cancer has spread beyond the layers of the colon and spread to the outer layers of the large intestine and some other surrounding tissue.
• T4a: The tumor has moved through all the layers of the colon at this stage.
• T4b: The tumor has spread to different organs and structures apart from the colon.

Node:

• NX: Regional lymph nodes cannot be examined.
• N0: No presence of colon cancer in regional lymph nodes.
• N1a: Tumor cells have been found in 1 regional lymph node.
• N1b: The presence of cancer cells is found in 2-3 regional lymph nodes.
• N1c: Nodules comprised of cancer cells have been discovered in structures near the colon which do not seem to be lymph nodes.
• N2a: Cancer cells are found in 4-6 regional lymph nodes.
• N2b: Cancer cells are found in more than 7 regional lymph nodes.

Metastasis:

• M0: parts of the body far away from the colon have not yet been affected by cancer.
• M1a: In addition to the colon, cancer has spread to one other part of the body.
• M1b: In addition to the colon, cancer has spread to more than one part of the body.
• M1c: In this stage, cancer has spread to the peritoneal surface.

Staging is one of the most useful tools that can be used when it comes to treating cancer cases. It can help in conveying a lot of information which allows both the doctors and patients to immediately understand what should be done next. It is safe to say that the treatments that are chosen for colon cancer depend heavily on the stage it is at.